Scraper attachment for power tool



Ma.rch 29, 1960 Filed Sept. 20, 1957 H. C. DUHOUX .SCRAPER ATTACHMENTFOR POWER TOOL 2 Sheets-Sheet 1 INVENTOR Henry CIDa/zoux BY M W IATTORNEYS March 29, 1960 H. c. DUHOUX 2,930,055

SCRAPER ATTACHMENT FOR POWER TOOL Filed Sept. 20, 1957 2 Sheets-Sheet 2NH .111 [III lll-llll .1" m! Illl jill-lpl m I [HI Hal I i INVENTORHenry C. Du/zoux BY M M W ATTORNEYS United States Patent 2,930,065SCRAPER ATTACHMENT FOR POWER T001.

Henry C. Duhoux, Alhambra, Calif.

Application September 20, 1957, Serial No. 685,196

8 Claims. (Cl. 15-236) This invention relates to a scraper attachmentfor a power tool for scraping the surfaces of hard materials such asconcrete, stucco, rock, asphalt, metal and the like to remove paint orto reface unpainted surfaces.

Removal of hardened paint from masonry surfaces is usually accomplishedby sand blasting techniques which involve the use of expensive equipmentand a large quantity of especially prepared sand. Sand blasting requiresa degree of skill and experience beyond that of the novice. In addition,there are certain difiiculties inherent in a sand blasting operationeven when professional operators are employed. For example, in refacingor removing paint from relatively soft stucco, such as extensively usedin the construction of western homes, the lack of control of thescraping action of the sand blast results in an uneven removal of thestucco surface, and wooden trim such as window sills and decorativegoings must be given a wide clearance to avoid defacing Power drivenwire brushes have also been used for this purpose, but these have atendency to rub or burn the paint into the pores of the surface ratherthan to scrape the paint off the surface. In addition, the general shapeof wire brushes prevents their engagement in irreg- Ellarities orcrevices commonly encountered in such suraces.

The major object of this invention is to provide a power tool attachmentfor scraping hard surfaces having a scraper with easily removable andadjustable scraping tufts.

Another object of this invention is to provide a power Another majorobject of this invention is to provide a power tool attachment forscraping hard surfaces which is effective up to the edge of wood windowcasings or other wood trim without damaging the wood.

Another object of this invention is to provide a power tool attachmentfor scraping hard surfaces which will perform the scraping operationuniformly over large areas.

In attaining these objects, one of the features of the invention residesin the arrangement of a plurality of scraping tufts radiating from a hubat angles greater than and less than 90 to the axis of the hub and whichare angularly spaced from each other about the hub at angles greaterthan 45.

Another feature of the invention resides in the construction of thescraping tufts, each of which has a plurality of superimposed sets offiat, elongate, spring steel scraping members side by side in planesparalleling the axis of rotation of the scraper.

Another feature of the invention resides in the scraper attachmentconstruction which includes a hub member and a cover member forretaining the scraping tufts at the desired angle relative to the axisof the hub and rigidly coupling them to the hub.

These and other objectsand advantages of the invention will becomeapparent from the following specification taken in connection with theaccompanying drawings wherein: f

Fig. l is a plan view of the scraper attachment for a power toolembodying the invention in its preferred form with one part broken awayand shown in section to show the assembly of one of the, scraping tufts;

Fig. 2 is a cross-sectional view of the scraper attachment attached to apower tool; 4

Fig. 3 is a partial sectional view of the scraping tuft and tuftretaining lug taken on line 33 of Fig. 2;

Fig. 4 is a side elevational view of one of the scraping tufts shown in,Figure 1; v

Fig. 5 is a plan view of the scraping tuft shown in Figure 4;

Fig. 6 is a plan view of a modified scraper attachment showing analternate arrangement of tufts in the hub;

Fig. 7 is a side view of one of the scraping tufts and tuft retaininglug sh )wn in Fig. 2.

As shown in Figures 1 and 2, the scraper attachment generally indicatedat 16, includes a hub member 12 and a cover member 14. Spaced about theperipheral margin of the hub member are a plurality of tuft receivingchambers 16 having a bottom wall 18 inclined to the axis of the hub andside walls 20 and 22 extending upwardly from the bottom wall 18. Betweenthe side walls 26 and 22, an end wall 24 extends upwardly from thebottom wall 18 defining a peripheral opening 2 6 on the peripheralmargin of the hub member 12. Projecting from the bottom wall anddisposed between the side walls 20 and 22 is a retaining element 28 thefunction of which will be explained in greater detail later in thespecification. Disposed between each of the chambers 16 is a removableretaining lug 30, constructed of a resilient material such as hardrubber, with side walls 32 and 34 and a partition 36 therebetweenextending from a base portion 44 to define channels 38 and 40 whichextend from the retaining element 28 toward the periphery of the hubmember 12 and in which scraping tufts 42 are inserted. As shown inFigure 7, the channels are of a depth sufiicient to isolate the scrapingtufts from the hub 12. In this way, vibration of the blades does notcause them to engage any part of the hub so that workhardening andresultant breaking is avoided. Similarly, to keep the blades fromcontact with the cover member 14, the resilient sheet 46 of neoprene ora like material, is placed over the top of the retaining lug 30 and thescraping'tuft therein. To lock the sheet 46 and the tuft 42 in place, asteel clip 48 overlies the sheet 46 and is secured to the retaining lug30 by tabs 50 and 52 which engage in grooves 54 and 56 extending thelength of the side walls 32 and 34.

' As best seen in Figure 7, the retaining lug 30 has an inclined face 58which rests against an inclined face 60 of the retaining element 28. Theback edge;62 andlthe front edge 64 of the lugs are disposed at an anglewith a shoulder 66 overhanging the end wall 24 of the hub member. 1,

Each of the tufts 42, as seen in Figures 4 and 5, is composed of aplurality of fiat, elongate, steel blades 68 arranged side by side insets 70 with several sets imposed one upon the other and bent at 72 intoa U-shape. .In the assembly, the tufts are inserted into the channels 38and 49 of the retaining lug 30, the resilient sheet 46 placed over them,and the steel clip 48 snapped into place. Each of the retaining lugs.and the tufts thus assembled are inserted into the chambers 16 in thehub with the bent portion 72 straddling the retaining elements 28.

Experience has shown that under normal conditions the tufts can beexpected to wear out after about one days operation. The replacement ofthe tufts isa'ccomplish'ed by removingscrews 74 and lifting off thecover member 14. Upon removal of the tufts and retaining lugs fromchamber 16, a newly assembled lug and tuft is inserted. The cover memberis then once "again secured to the hub member and the scraper .is readyfor use. The retaining lug is composed of a resilientmaterial which actsas a bushing to'reduce severity of the vibration effect associated withthe tufts under operating conditions.

Closing each of the chambers 16 and retaining the tufts 42 therein by aclosure wall 76 and side walls 78 and 80, is the cover member 14 whichrests on the hub member 12 and is secured thereto by the screws 74. Thehub is adapted to be coupled to the power tool 82 through athreadedopening 84 located at the center of the cover member whichaccommodates the threaded driving shaft =86 of the power tool.

As best seen in Figure 1, the center line of these cham 'bers 16 lies ona line spaced from and parallel to a radial line of the hub.

According to the present invention, the tuft leg portions each lie in aplane parallel to a radial axial plane of the hub, and the leg portionsalso lie in a plane at an angle of greater than 45 and less than 90 tothe hub 'axis. The tuft leg portions each lie longitudinally edgewise onthe surface of a cone having its apex at the hub axis and having anincluded apex angle greater than 90 and less than 180. The scrapingelements are arranged ingroups of individual U-shaped tufts, the groupsbeing angularly spaced from one another about the hub at angles ofgreater than 45.

In use, the approximate circle of rotation at the end 'of the tuft isinclined at an acute angle with respect to the surface to be scraped tocreate a more effective scraping action. To control the severity of thescraping action, this angle of inclination or attack may be adjusted bythe operator. This permits the effective scraping of the sur- "faceright up to an edge of a wooden window casing or other similar marginswithout damaging the wood or ex- "ceeding the margin. Furthermore, withone side of the circle of rotation of the tuft engaging the surface tobe scraped, the upward lift of such engagement is normally sufficient tocarry most of the weight of the apparatus so that an operator needprovide only a sufficient force "to guide the apparatus to control thedegree of scraping.

The fiat of each blade is arranged to face in the direc- "tion oftherotation of the hub so that the tufts are relatively flexible in thedirection around the circle of rotation and relatively rigid in thedirection of the axis of "rotation. The flexibility and spacing of thetufts around the circle of rotation causes them to engage the surface"with a severe whipping action which chips the surface. 'Thechippingaction increases with the increased inclination of the circle ofrotation of the ends of the tufts with respect to the surface beingscraped, which effect produces chick and easy control of the degree ofscraping, the degree of control being enhanced by the relative rigidityof 'thetufts in the direction approximately parallel to the axisofrotation.

In operation, the vibration effects associated with each tuft are verysevere. When metal tufts are used, there have been instances ofpremature failure of the tufts befcause of crystallization of the bladesnear the point where they extend out of the lug. Furthermore, theoperator of the apparatus is subjected to a considerable amount ofvibration. By constructing the lugs from a resilient mater'ial, such ashard rubber, it has been found that the lugs act both as .a shockabsorber between the blades and the operator, and also prevent failureof the blades because of crystallization.

The blades of the tufts are preferably made of spring steel and thegreatest success has been found by using flat, elongate blades. Alsofiat blades are the easiest to insert in'the retaining 'lugs. Thescraper attachment is of 4 great value in removing welding fluxandspatter as well as paint and rust from metal surfaces.

The modification of the power tool attachment as seen in Figure 6 showsthe center of the tuft lying in the same plane as a radius of the hub.Although the tool performs effectively when the tufts are so positioned,experience has shown that offsetting the tufts as shown in Figure 1stops chattering of the scraper and permits the tool to be used flatagainst the surface without inclining the tool at an acute angle withrespect to the surface to be scraped if it is so desired.

While only two embodiments of applicants invention have been disclosed,it will be apparent to those skilled in the art that various changes andmodifications coming within the scope of the invention are to beincluded in the appended claims.

What I claim as my invention is:

1..A scraper attachment for a power tool comprising a hub rotatableabout its axis by a power tool and a plurality of groups, of individualU-shaped scraping tufts carried by said hub and projecting therebeyond,each of said tufts having bight portions fixedly secured to said hub forrotation therewith and leg portions also rotatable with said hub andelongated in a plane parallel to a radial, axial plane of the hub axisand said tuft legs each lying longitudinally edgewise on the surface ofa cone having its apex at said axis and the included apex angle of saidcone being greater than and less than said tuft groups being angularlyspaced from one another about said hub at angles greater than 45.

2. A scraper attachment as defined in claim 1, wherein resilientlydeformable shock-absorbing means are interposed between the leg portionsof each group of tufts and the hub to isolate the hub assembly from thevibration of the leg portions during working.

3. A scraper attachment for a power tool comprising a hub assemblyrotatable about its axis by a power tool, said hub assembly comprising ahub member and a cover member secured together to cooperatively define aplurality of peripherally spaced individual recesses, and means on oneof said members defining rigid retaining elements projecting into eachof said recesses, respectively; scraping tufts anchored in each of saidrecesses, said tufts each comprising a plurality of nested, fiat,elonate, steel blades of U-shaped configuration having bight portionslapping said retaining elements and leg portions projecting beyond'saidrecesses, said tuft leg portions each lying in a plane parallel to aradial, axial plane of the hub and lying longitudinally edgewise on thesurface of a cone having its apex at said axis and the included apexangle being greater than 90 and less than 180; and resilientlydeformable shock-absorbing means interposed between the leg portions ofsaid tufts and said hub assembly radially outwardly of said retainingmeans.

4. A scraper attachment as defined in claim 3, wherein said members arecircular in configuration and the peripherally spaced recesses definedthereby are offset from, but parallel to, radii of said members.

5. A scraper attachment as defined in claim 3, wherein saidshock-absorbing means comprises an elastomeric block having parallelgrooves in which said tuft leg portions are confined and means closingthe grooves and interposed between one of said members and said block.

6. A scraper attachment for a power tool comprising a hub assemblyrotatable about its axis by a power tool, said hub assembly comprising ahub member and a cover member secured together to cooperatively define aplurality of peripherally spaced separate recesses, and means on one ofsaid members defining fixed retaining elements projecting into each ofsaid recesses, respectively; scraping tufts anchored in each of saidrecesses, said tufts each comprising a plurality of nested, fiat,elongate, steel blades of U-shaped configuration having bight portionslapping said fixed retaining elements and leg portions projecting fromsaid recesses beyond the hub assembly each such tuft leg being elongateto lie in a plane parallel to a radial, axial plane of the hub axis andsaid leg also lying in a plane at an angle of greater than 45 and lessthan 90 to said axis; and resilient lugs disposed in said recesses,respectively, to substantially fill said recesses radially outwardly ofsaid retaining elements and having grooves in which the tuft blades areseated, said resilient lugs having groove-defining portions interposedbetween said hub assembly and said tuft legs to prevent contacttherebetween to isolate the hub assembly from the vibration of the tuftlegs during Working.

7. A scraper attachment as defined in claim 6 wherein the grooves insaid resilient lugs are closed by clips interposed between one of saidmembers and said resilient lugs.

8. For use with a power tool scraper attachment, a scraping tuftcomprising a plurality of adjacent, aligned stacks of nested U-shapedblades each having substantially parallel planar scraper legs joined bya medial bent portion, the planar legs of adjacent blades in each stackbeing in extended surface contact for mutual reinforcego ment, thealigned edges of the medial bent portions and of the legs of the bladesin adjacent stacks being in extended contact with one another for mutualtransverse reinforcement, whereby the blade legs are mutuallyreinforced, but individually flexible, in all directions.

References Cited in the file of this patent UNITED STATES PATENTS1,497,921 Levedahl June 17, 1924 1,650,035 Peterson Nov. 22, 19271,967,651 Anderson July 24, 1934 2,178,169 Goertzen Oct. 31, 19392,241,845 Chapman May 13, 1941 2,523,319 Middlestadt Sept. 26, 19502,552,382 Root May 8, 1951 2,565,047 Rowland Aug. 21, 1951 2,740,980Asbury Apr. 10, 1956 2,763,257 Asbury Sept. 18, 1956 FOREIGN PATENTS528,587 France Aug. 20, 1921

